Isolation and identification of Pseudoxanthomonas winnipegensis from blood culture by MALDI-MS

Pseudoxanthomonas is a genus primarily isolated from environmental samples and causes opportunistic infections. In this study, we conducted a detailed investigation of P. winnipegensis, which was isolated for the first time from a blood sample in Japan in 2022, and evaluated five Pseudoxanthomonas species, including P. kaohsiungensis, P. japonensis, P. mexicana, P. spadix and P. winnipegensis, that cause human infections. However, it is difficult to identify accurately by routine microbiological testing. Our analysis revealed that matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) classification is feasible when using the mass peaks corresponding to ribosomal proteins L29 and L33, as well as the cold-shock protein CspA, as marker peaks. These findings indicate the potential of MALDI-MS for the rapid and reliable detection of Pseudoxanthomonas species in routine microbiological diagnostics.